The invention relates to a detecting arrangement used in liquid chromatography for the analysis of a selected non-volatile phase of a liquid effluent.
Detecting arrangements in most common use in the field of liquid chromatography are the so-called transport detectors. The main part of a transport detector is a mechanical conveyor (embodied, e.g. by a wire, band, chain or rotating grid) to which the effluent is applied. Such effluent is transmitted by the conveyor from a source of the effluent (e.g. a column of the liquid chromatograph) to a separator, where the volatile phase is separated from the desired component to be analyzed. The conveyor thereupon carries the desired component to a gasifier, and the resulting gasified component is introduced to a sensing device (e.g. a pair of electrodes). The response of the sensing device to the passage of the selected components is thereupon registered by a recorder connected electrically with the electrodes for further analysis.
One disadvantage of such arrangements when used in liquid chromatography is that they have a sensitivity which is at best 2-4 orders lower than that obtainable in gas chromatography measurements using the same sensors. Moreover, such arrangements cannot effect a high degree of gasification of the selected phase, so that the usable sample of the selected component introduced to the sensor is small; this is particularly true if the conveyor is not completely wetted by the effluent.
Additionally, problems have been found to occur with the conveyor of the transport detector regarding its cleaning, its preparation for the repeated transmission of samples to be analyzed, and in the selection of its materials for the good mechanical and heat resistant properties necessary to accommodate its repeated passage through the hot gasification zone. Also, in this connection facilities must be provided to assure a constant rate of advance of the conveyor.